Integrated hybrid compact fluid heat exchanger

ABSTRACT

An Integrated Hybrid Compact Fluid Heat Exchanger is disclosed. An example embodiment includes: a micro-channeled plate for a stream of a working fluid, the micro-channeled plate being diffusion bonded or brazed with a cover plate; and a fin assembly brazed, diffusion bonded, or welded to the micro-channeled plate. Other embodiments include a fan or blower coupled to the Integrated Hybrid Compact Fluid Heat Exchanger via air ducting or close coupling.

PRIORITY PATENT APPLICATION

This patent application is a non-provisional patent application drawing priority from U.S. provisional patent application Ser. No. 63/044,948; filed Jun. 26, 2020. This present non-provisional patent application draws priority from the referenced patent application. The entire disclosure of the referenced patent application is considered part of the disclosure of the present application and is hereby incorporated by reference herein in its entirety.

COPYRIGHT

A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction of the patent document or the patent disclosure, as it appears in the U.S. Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to the disclosure provided herein and to the drawings that form a part of this document: Copyright 2018-2021, Vacuum Process Engineering, Inc.; All Rights Reserved.

TECHNICAL FIELD

The disclosed subject matter relates to the field of heat exchangers, heat exchanging devices, and methods of making a heat exchanging device, which can form complex, three dimensional geometrical configurations; and to a method of constructing a heat exchanging device formable into a predetermined configuration, and in particular, to an Integrated Hybrid Compact Fluid Heat Exchanger.

BACKGROUND

Often, an operating machine or electronic component or an industrial process system generates waste heat in the course of its normal operation. If this waste heat is not removed, degraded performance or damage to the system may result. Frequently, the operating temperature of a system needs to be precisely maintained in order to obtain optimal performance. For example, it is often desirable to cool the sensors used in thermal imaging cameras to improve the sensitivity of the imager. Further, analytical instruments may require that the sample to be analyzed be presented to the instrument at a precisely controlled temperature. Additionally, heat exchangers are important in concentrating solar thermal power (CSP) systems.

Heat exchangers permit heat to be removed or added to the sample as may be desired. A common type of heat exchanger is referred to as a “heat sink.” A heat sink typically transfers heat between a solid object and some fluid media, which may a liquid, air or other gasses. Computer microprocessors frequently employ heat sinks to draw heat from the processor to the surrounding air, thereby cooling the microprocessor. Fins are often provided to increase the surface area of the heat sink to the air thereby increasing the efficiency of the heat sink. Such a heat sink could also comprise a closed fluid system. For example, a recirculating liquid coolant might be used to transfer heat from that portion of the heat sink in contact with the heat-generating device to a remotely located radiator. The heat sink could be of a single or a two-phase fluid design.

Another type of heat exchanger employs at least two fluids. In this type of heat exchanger, heat is transferred from a first fluid to a second fluid without direct contact between the fluids. For example, a fluid-to-fluid heat exchanger for a blood processing machine may employ heated water to warm the blood to the proper temperature. The blood circulating path is completely separate from that of the water circulating path and dilution or contamination of the blood is thus avoided. Other types of heat exchangers include those designed to recover waste heat from systems that produce excess heat, for example, a passenger compartment heater that derives heat from an automobile engine. Regardless of the type of heat exchanger, it is desirable to obtain a high degree of heat transfer efficiency.

The basic function of a heat exchanger is to convey heat from one location to another. While some heat exchangers are relatively simple, such as that of a cast aluminum heat sink for a semiconductor, others are quite complex and require a variety of sophisticated manufacturing processes. For example, some manufacturing processes use diffusion bonding to combine layers of a heat exchanger. Other manufacturing processes can use brazing to combine a stack of planar members to produce heat exchangers. These processes permit the construction of very intricate internal structures. In the case of a heat exchanger or chemical reactor produced by these means, it is necessary to provide ports so the heat exchanging fluids or reactant chemicals can be hermetically ported into and out of the device proper. However, conventional systems and fabrication processes have been unable to efficiently manufacture these structures.

SUMMARY

There is disclosed herein various example embodiments of an Integrated Hybrid Compact Fluid Heat Exchanger. As used herein, the term “fluid” includes air, gas, or plasmas, which can be used as working fluids within example embodiments of the heat exchanger as described herein. In example embodiments, a Hybrid Compact Fluid Heat Exchanger comprises a diffusion bonded or brazed micro-channeled plate for a working fluid (e.g., supercritical carbon dioxide (sCO2) power cycles) brazed, diffusion bonded, or welded in an assembly with a heatsink fin pad to form the Hybrid Compact Fluid Heat Exchanger. The Hybrid Compact Fluid Heat Exchanger can then be combined with an axial or centrifugal fan and air-side ducting or close coupling to form an Integrated Hybrid Compact Fluid Heat Exchanger. The various example embodiments are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which:

FIG. 1 illustrates an example embodiment of an Integrated Hybrid Compact Fluid Heat Exchanger in a perspective view;

FIG. 2 illustrates an example embodiment of the various layers forming a Hybrid Compact Fluid Heat Exchanger in a side view;

FIG. 3 illustrates an example embodiment showing an exploded view of the various layers forming the integrated assembly of a Hybrid Compact Fluid Heat Exchanger;

FIG. 4 illustrates an example embodiment showing the brazed layers of a Hybrid Compact Fluid Heat Exchanger;

FIG. 5 illustrates an example embodiment showing a detail of the fins and micro-channels of a Hybrid Compact Fluid Heat Exchanger;

FIGS. 6A through 6C illustrate various example embodiments showing several different layout patterns of the micro-channeled plate;

FIG. 7 illustrates various example embodiments showing several different heatsink fin configurations;

FIG. 8 illustrates a conventional backward curved centrifugal fan or blower that can be used with an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger;

FIG. 9 illustrates an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger with a centrifugal fan or blower;

FIG. 10 illustrates an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger with an axial fan;

FIG. 11 illustrates an exploded view of an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger with an axial fan;

FIG. 12A illustrates an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger with a blower in a flat configuration;

FIG. 12B illustrates an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger with a blower in an angled configuration;

FIG. 13 illustrates an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger configured for multiple fans in a flat configuration; and

FIG. 14 is a flow diagram illustrating an example embodiment of a method for fabricating an Integrated Hybrid Compact Fluid Heat Exchanger as described herein.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which are shown, by way of illustration, specific embodiments in which the disclosed subject matter can be practiced. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the disclosed subject matter.

In various example embodiments disclosed and illustrated herein, an Integrated Hybrid Compact Fluid Heat Exchanger is described. In example embodiments, the basic structure of the described Hybrid Compact Fluid Heat Exchanger comprises a diffusion bonded or brazed micro-channeled plate for a working fluid (e.g., supercritical carbon dioxide (sCO2) power cycles) brazed, diffusion bonded, or welded in an assembly with a heatsink fin pad to form a Hybrid Compact Fluid Heat Exchanger. The Hybrid Compact Fluid Heat Exchanger can then be combined with an axial or centrifugal fan and air-side ducting or close coupling to form an Integrated Hybrid Compact Fluid Heat Exchanger.

Referring to FIG. 1, an example embodiment of an Integrated Hybrid Compact Fluid Heat Exchanger 100 in a perspective view is illustrated. A Hybrid Compact Fluid Heat Exchanger of an example embodiment is an innovative, compact heat exchanger for use with a working fluid, such as supercritical carbon dioxide (sCO2) power cycles. In other embodiments, other working fluids may also be used, including molten salt, liquid metals, etc. In fact, any working fluid that is high pressure and potentially corrosive (where the containment requires a higher grade material) and/or where small micro-channels are used for better containment of high pressure can benefit from the construction of the Hybrid Compact Fluid Heat Exchanger as described herein. The Hybrid Compact Fluid Heat Exchanger can include a high-efficiency centrifugal blower or axial fan and air-side ducting or close coupling to minimize power consumption and decrease maintenance costs. Additionally, a hybrid concept of combining diffusion bonded or brazed microchannel heat exchanger (MCHE) geometry for the working fluid stream and brazed, diffusion bonded, or welded plate-fin geometry for the air stream allows for enhanced heat exchange between the streams, accommodating the large mismatch in fluid properties between air and the working fluid. To reduce manufacturing costs, the Hybrid Compact Fluid Heat Exchanger internal components can be assembled with a combination of brazed, diffusion-bonded, or welded elements, enabling optimal material selection for each stream. MCHE geometries and flow patterns are optimized to provide maximum heat transfer efficiency between the hot and cold streams. Additionally, using micro flow channels allows for a large interface surface area between streams while maintaining an overall compact design. In particular embodiments, the Integrated Hybrid Compact Fluid Heat Exchanger as described herein has a potential effectiveness of 90% or higher, depending on economics (as compared to 60% maximum for a conventional crossflow, fin-fan dry cooler).

Referring now to FIG. 2, an example embodiment of the various layers forming the Hybrid Compact Fluid Heat Exchanger in a side view is illustrated. The example embodiment uses formed fins for the air side and etched plates for the working fluid side. As shown, a micro-channeled plate 220 is created to provide micro-channels for the flow of the working fluid stream. The micro-channeled plate 220 for the working fluid stream can be fabricated using a chemical subtractive process, built using an additive process, or cut to pre-determined dimensions using a laser or laser-based process. Depending on the fabrication process used, both a top and bottom cover sheet may be required. In other embodiments, the micro-channeled plate 220 can be fabricated using: electrochemical machining (ECM), electrical discharge machining (EDM), computer numerical controlled (CNC) machining, mechanical machining, grinding, or the like. As described in more detail below, the pattern etched on the micro-channeled plate 220 can employ various flow configurations, including counter-flow and multi-pass arrangements, to increase heat transfer while maintaining a compact design. Referring still to FIG. 2, a blank cover plate or sheet 210 can be placed over the micro-channeled plate 220 to close the micro channels within the assembly. The blank cover plate 210 can be diffusion bonded or brazed to the micro-channeled plate 220 to create a diffusion bonded or brazed micro-channeled plate assembly 230 having broad and compact surface area for better heat transfer between the blank cover plate 210 and the micro-channeled plate 220. In various example embodiments, the material from which the micro-channeled plate 220 is fabricated can include: stainless steel alloys, SS300 series, titanium, nickel alloys, ferretics, or carbon steel.

Referring still to FIG. 2, the Hybrid Compact Fluid Heat Exchanger can include a heatsink fin pad 242 with side bars 244 combined in a fin assembly 240. The fin assembly 240 provides a plate-fin geometry for the air stream of the Hybrid Compact Fluid Heat Exchanger. As described in more detail below, the plate-fin geometry of the fin assembly 240 can be configured in various patterns to produce better heat transfer between the fin assembly 240 and the diffusion bonded or brazed micro-channeled plate assembly 230. In an example embodiment, the fin assembly 240 can be brazed, diffusion bonded, or welded to the diffusion bonded or brazed micro-channeled plate assembly 230 to produce a combined micro-channeled plate and fin assembly 250. Multiple brazed or diffusion bonded micro-channeled plate and fin assemblies 250 can be stacked and brazed or diffusion bonded together to form the Hybrid Compact Fluid Heat Exchanger 260.

The Hybrid Compact Fluid Heat Exchanger 260 can be assembled with a combination of brazed, diffusion-bonded, or welded elements. The use of diffusion bonding or brazing for the diffusion bonded or brazed micro-channeled plate assembly 230 creates a beneficial and thermally efficient interface and surface for thermal transfer between the blank cover plate 210 and the micro-channeled plate 220. The use of brazing, diffusion-bonding, or welding for the micro-channeled plate and fin assemblies enables the integration of the stacked micro-channeled plate and fin assemblies without damaging the fin structure.

Within the Hybrid Compact Fluid Heat Exchanger, a hybrid concept of combining diffusion bonded or brazed MCHE geometry for the working fluid stream and brazed, diffusion bonded, or welded plate-fin geometry for the air stream maximizes the potential heat transfer between the streams, lowering compressor inlet temperatures, and increasing cycle efficiencies. The combination of manufacturing techniques is significant because it allows for different materials to be used for the working fluid stream and the air stream. Because of the high pressures, high temperatures, and highly corrosive nature of the working fluid (e.g., sCO2), high-grade materials must be used to manufacture all geometries that are directly contacting and containing the working fluid stream. The combination of manufacturing techniques as described herein allows for lower-grade materials with higher thermal conductivities to be used for the air-side geometries. This solution allows for increased heat transfer, as well as, reduced manufacturing costs.

FIG. 3 illustrates an example embodiment showing an exploded view of the various layers forming the integrated assembly of a Hybrid Compact Fluid Heat Exchanger. As shown, the micro-channeled plate 220, the blank cover plate 210, and the fin assembly 240 can be integrated to form the Hybrid Compact Fluid Heat Exchanger. FIG. 4 illustrates an example embodiment showing the brazed, diffusion bonded, or welded layers of a Hybrid Compact Fluid Heat Exchanger. The side ports 410 for the working fluid stream and the fin structures 420 are also shown. FIG. 5 illustrates an example embodiment showing a detail of the fins and micro-channels of a Hybrid Compact Fluid Heat Exchanger.

FIGS. 6A through 6C illustrate various example embodiments showing several different alternative layout patterns of the micro-channeled plate 220. The plates for the working fluid side can be fabricated using a chemical subtractive process, built using an additive process, or cut to pre-determined dimensions using a laser or laser-based process. This design can also employ various flow configurations, including counter-flow and multi-pass arrangements, to increase heat transfer while maintaining a compact design. FIG. 6A illustrates an example of a multi-pass etched micro-channel arrangement. FIG. 6B illustrates an example of a multi-pass etched micro-channel arrangement with an integral header. FIG. 6C illustrates an example of a counter-flow etched micro-channel arrangement. It will be apparent to those of ordinary skill in the art in view of the disclosure herein that other alternative layout patterns of the micro-channeled plate 220 can be equivalently used.

FIG. 7 illustrates various example embodiments showing several different heatsink fin configurations. By using formed fins, the need for etching the air side heatsink fins (half the number of total layers) is avoided. The formed fins can be optimized to produce better heat transfer to pressure drop ratio, using various types of fin configurations as shown in FIG. 7 (e.g., herringbone, louvered, lanced, perforated, plain, etc.). Such fin configuration options cannot be used in the conventional state-of-the-art dry coolers in the market, which use finned tubes. To optimize the aerothermal performance on the air side of the Hybrid Compact Fluid Heat Exchanger, any of the various fin geometries, including plain plate fins, serrated fins, perforated fins, louvered fins, and herringbone fins may be used. This is a significant improvement as compared to fin-fan coolers where only the fin height and pitch can be varied. In various example embodiments, the material from which the fins are fabricated can include: aluminum, copper, titanium, carbon steel, or nickel alloys.

FIG. 8 illustrates a conventional backward curved centrifugal fan or blower that can be used with an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger. As described below, conventional axial fans can also be used to provide the air flow for the Integrated Hybrid Compact Fluid Heat Exchanger.

FIG. 9 illustrates an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger with a centrifugal fan or blower. A centrifugal blower can be included to drive the cooling airflow through the Hybrid Compact Fluid Heat Exchanger. Air from the blower can be directed through a transitional duct from the blower exit into the Hybrid Compact Fluid Heat Exchanger. This setup provides several operational benefits. First, using a controlled airflow volume will reduce the inefficiencies due to air-maldistribution across heat exchanger geometry. Additionally, the outer duct/housing will provide environmental protection for the air-side geometry, reducing the risk of corrosion and fouling on the fins. The driver system and bearings can be configured to minimize associated losses. To reduce environmental effects on Hybrid Compact Fluid Heat Exchanger performance, the cooling air can be filtered at the blower inlet and directed through a transitional duct between the blower and the heat exchanger. The filter and transitional ducting will minimize contaminant exposure, reducing the likelihood of blockage or fouling. This will provide a reduction in maintenance needs and improved system stability. Furthermore, minimizing the amount of downtime to service auxiliary equipment improves grid reliability. To maintain high-efficiency operation, the blower impeller and housing can be optimized to maximize aerodynamic efficiency for particular applications. The aerodynamic and mechanical design of the blower and transitional ducting can be configured to optimize the aerodynamics while maintaining high mechanical reliability. The blower design can also consider the cost-efficiency sensitivity to determine a configuration that minimizes the expected levelized cost of electricity (LCOE). Additionally, the fan blower/motor system may be driven with a variable frequency drive motor to increase efficiency. In this case, motor operation may be controlled to optimal efficiency through a feedback loop with input from ambient temperature or other parameters. In a particular embodiment, the Integrated Hybrid Compact Fluid Heat Exchanger with a fan/blower can be used in concentrating solar power (CSP) plants for thermal management.

FIG. 10 illustrates an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger with an axial fan. FIG. 11 illustrates an exploded view of an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger with an axial fan. As with the centrifugal blower implementation described above, the axial fan implementation of an example embodiment can include transitional ducting or close coupling from the axial fan exit into the Hybrid Compact Fluid Heat Exchanger.

FIG. 12A illustrates an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger with a blower in a flat configuration. FIG. 12B illustrates an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger with a blower in an angled configuration. FIG. 13 illustrates an example embodiment of the Integrated Hybrid Compact Fluid Heat Exchanger configured for multiple fans in a flat configuration. Depending upon the physical constraints of a particular facility, the ambient temperatures, the required efficiency level, the cost of power, and other factors, the configuration of the Integrated Hybrid Compact Fluid Heat Exchanger may need to be varied, as shown in FIGS. 9 through 13 to accommodate the needs of a particular application or location. In any case, the Hybrid Compact Fluid Heat Exchanger and integrated blower/fan assemblies can provide an efficient and cost-effective solution for thermal management.

FIG. 14 is a flow diagram illustrating an example embodiment of a method for fabricating an Integrated Hybrid Compact Fluid Heat Exchanger as described herein. The method 1000 of an example embodiment includes: diffusion bonding or brazing a micro-channeled plate for a stream of a working fluid with a cover plate (processing block 1010); and diffusion bonding, brazing, or welding a fin assembly to the micro-channeled plate (processing block 1020).

The illustrations of embodiments described herein are intended to provide a general understanding of the structure of various embodiments, and they are not intended to serve as a complete description of all the elements and features of components and systems that might make use of the structures described herein. Many other embodiments will be apparent to those of ordinary skill in the art upon reviewing the description provided herein. Other embodiments may be utilized and derived, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. The figures herein are merely representational and may not be drawn to scale. Certain proportions thereof may be exaggerated, while others may be minimized. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

The description herein may include terms, such as “up”, “down”, “upper”, “lower”, “first”, “second”, etc. that are used only for descriptive purposes and not to be construed as limiting. The elements, materials, geometries, dimensions, and sequence of operations may all be varied for particular applications. Parts of some embodiments may be included in, or substituted for, those of other embodiments. While the foregoing examples of dimensions and ranges are considered typical, the various embodiments are not limited to such dimensions or ranges.

The Abstract is provided to allow the reader to quickly ascertain the nature and gist of the technical disclosure. The Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In the foregoing Detailed Description, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments have more features than are expressly recited in each claim. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.

As described herein, an Integrated Hybrid Compact Fluid Heat Exchanger is disclosed. Although the disclosed subject matter has been described with reference to several example embodiments, it may be understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the disclosed subject matter in all its aspects. Although the disclosed subject matter has been described with reference to particular means, materials, and embodiments, the disclosed subject matter is not intended to be limited to the particulars disclosed; rather, the subject matter extends to all functionally equivalent structures, methods, and uses such as are within the scope of the appended claims. 

What is claimed is:
 1. An Integrated Hybrid Compact Fluid Heat Exchanger comprising: a micro-channeled plate for a stream of a working fluid, the micro-channeled plate being diffusion bonded or brazed with a cover plate; and a fin assembly brazed, diffusion bonded, or welded to the micro-channeled plate.
 2. The Integrated Hybrid Compact Fluid Heat Exchanger of claim 1 further including a second cover plate being diffusion bonded or brazed with the micro-channeled plate.
 3. The Integrated Hybrid Compact Fluid Heat Exchanger of claim 1 wherein the micro-channeled plate is fabricated from a material from the group consisting of: stainless steel alloys, SS300 series, titanium, nickel alloys, ferretics, and carbon steel.
 4. The Integrated Hybrid Compact Fluid Heat Exchanger of claim 1 wherein the fin assembly is fabricated from a material from the group consisting of: aluminum, copper, titanium, carbon steel, and nickel alloys.
 5. The Integrated Hybrid Compact Fluid Heat Exchanger of claim 1 wherein the micro-channeled plate is fabricated using a process from the group consisting of: chemical etching, an additive process, a laser-based process, electrochemical machining (ECM), electrical discharge machining (EDM), computer numerical controlled (CNC) machining, mechanical machining, and grinding.
 6. The Integrated Hybrid Compact Fluid Heat Exchanger of claim 1 further including a fan or blower coupled to the Integrated Hybrid Compact Fluid Heat Exchanger via air ducting or close coupling.
 7. The Integrated Hybrid Compact Fluid Heat Exchanger of claim 6 wherein the fan or blower is of a type from the group consisting of: a centrifugal blower and an axial fan.
 8. The Integrated Hybrid Compact Fluid Heat Exchanger of claim 1, wherein the working fluid is from the group consisting of: supercritical carbon dioxide (sCO2), molten salt, and liquid metals.
 9. The Integrated Hybrid Compact Fluid Heat Exchanger of claim 1, wherein the micro-channeled plate is diffusion bonded with the cover plate.
 10. The Integrated Hybrid Compact Fluid Heat Exchanger of claim 1, wherein the fin assembly is brazed or welded to the micro-channeled plate.
 11. A method for fabricating an Integrated Hybrid Compact Fluid Heat Exchanger, the method comprising: diffusion bonding or brazing a micro-channeled plate for a stream of a working fluid with a cover plate; and diffusion bonding, brazing, or welding a fin assembly to the micro-channeled plate.
 12. The method of claim 11 further including diffusion bonding or brazing a second cover plate with the micro-channeled plate.
 13. The method of claim 11 wherein the micro-channeled plate is fabricated from a material from the group consisting of: stainless steel alloys, SS300 series, titanium, nickel alloys, ferretics, and carbon steel.
 14. The method of claim 11 wherein the fin assembly is fabricated from a material from the group consisting of: aluminum, copper, titanium, carbon steel, and nickel alloys.
 15. The method of claim 11 wherein the micro-channeled plate is fabricated using a process from the group consisting of: chemical etching, an additive process, laser etching, electrochemical machining (ECM), electrical discharge machining (EDM), computer numerical controlled (CNC) machining, mechanical machining, and grinding.
 16. The method of claim 11 further including coupling a fan or blower to the Integrated Hybrid Compact Fluid Heat Exchanger via air ducting or close coupling.
 17. The method of claim 16 wherein the fan or blower is of a type from the group consisting of: a centrifugal blower and an axial fan.
 18. The method of claim 11, wherein the working fluid is from the group consisting of: supercritical carbon dioxide (sCO2), molten salt, and liquid metals.
 19. The method of claim 11, wherein the micro-channeled plate is diffusion bonded with the cover plate.
 20. The method of claim 11, wherein the fin assembly is brazed or welded to the micro-channeled plate. 